Coronary arteriography is a valuable and widely used clinical procedure for the diagnosis and treatment planning of chronic heart disease. In approximately 1 percent of the clinical procedures ventricular fibrillation occurs as a result of the injection of radiopaque contrast material. The objective of this project is to more clearly define the factors which promote ventricular fibrillation. Work in our laboratory has already demonstrated that Ca ions binding agents found in currently used contrast media increase the incidence of fibrillation in animal experiments. The radiopaque molecule itself binds Ca ions and we are currently quantifying the kinetics of this reaction. Contrast media are injected as very concentrated solutions and therefore cause large and rapid shifts in water and in electrolyte concentrations. Experiments using isolated perfused organs are currently being performed to quantify these shifts and their importance in promoting ventricular fibrillation. Acute and chronic ischemic heart disease and digitalis drugs have been shown to increase the tendency for fibrillation. We are currently performing animal experiments to determine if there is an interaction between these factors and coronary arteriography which would promote ventricular fibrillation. A clearer definition of factors promoting fibrillation will enable better identification of patients with high risk and also enable us to develop better contrast media.